136561-53-0Relevant articles and documents
Utilization of (18-Crown-6)-2,3,11,12-tetracarboxylic Acid as a Chiral NMR Solvating Agent for Diamines and β-Amino Acids
Rodriguez, Yolanda C.,Duarte, Tayla M.,Szakonyi, Zsolt,Forr?, Eniko,Fül?p, Ferenc,Wenzel, Thomas J.
, p. 708 - 715 (2015)
The compound (18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated as a chiral nuclear magnetic resonance (NMR) solvating agent for a series of diamines and bicyclic β-amino acids. The amine must be protonated for strong association with the crown ether. An advantage of (18-crown-6)-2,3,11,12-tetracarboxylic acid over many other crown ethers is that it undergoes a neutralization reaction with neutral amines to form the protonated species needed for binding. Twelve primary diamines in neutral and protonated forms were evaluated. Diamines with aryl and aliphatic groups were examined. Some are atropisomers with equivalent amine groups. Others have two nonequivalent amine groups. Association equilibria for these systems are complex, given the potential formation of 2:1, 1:1, and 1:2 crown-amine complexes and given the various charged species in solution for mixtures of the crown ether with the neutral amine. The crown ether produced enantiomeric differentiation in the 1H NMR spectrum of one or more resonances for every diamine substrate. Also, a series of five bicyclic β-amino acids were examined and (18-crown-6)-2,3,11,12-tetracarboxylic acid caused enantiomeric differentiation in the 1H NMR spectrum of three or more resonances of each compound. Chirality 27:708-715, 2015.
Enantioselective hydrolysis of 3,4-disubstituted β-lactams. An efficient enzymatic method for the preparation of a key Taxol side-chain intermediate
Galla, Zsolt,Beke, Ferenc,Forró, Eniko,Fül?p, Ferenc
, p. 107 - 112 (2015/12/01)
3,4-Disubstituted β-lactams 3-benzyloxy-4-(4-chlorophenyl)azetidin-2-one [(3S?,4R?)-(±)-1], 3-benzyloxy-4-phenylazetidin-2-one [(3S?,4R?)-(±)-2] and 4-(4-chlorophenyl)-3-phenoxyazetidin-2-one [(3S?,4R?)-(±)-3] were resolved through immobilized CAL-B-catalysed ring-cleavage reactions. Excellent enantioselectivities (E > 200) were obtained for (3S?,4R?)-(±)-1 and (3S?,4R?)-(±)-2 when the reactions were performed with added H2O as nucleophile in tert-butyl methyl ether at 70 °C, whereas only moderate E (12) was achieved for (3S?,4R?)-(±)-3 under the same conditions but in diisopropyl ether. The resulting ring-opened β-amino acids [(2R,3S)-4 (ee > 98%), (2R,3S)-5 (ee > 98%) and (2R,3S)-6 (ee = 50%)] and the unreacted β-lactams [(3S,4R)-1-3] (ee > 98%) could be easily separated.
New enzymatic two-step cascade reaction for the preparation of a key intermediate for the taxol side-chain
Forro, Enikoe,Fueloep, Ferenc
experimental part, p. 3074 - 3079 (2010/08/07)
Enzymatic strategies are reported for the synthesis of (2R, 3S)-3-amino-2-hydroxy-3-phenylpropionic acid (ee > 98%), a key intermediate of the side-chain of Taxolby enzymatic hydrolysis in organic media. The new enzymatic cascade reaction, which took place through Candida antarctica lipase B-catalysed deacylation followed by lactam ring-opening of racemic cis-3-acetoxy-4-phenylazetidin-2-one with H2O in iPr2O at: 60 °C, resulted in two different enantiopure products (ee ≥ 98%), one of them being the desired key intermediate for the side-chain of Taxol.